How big a threat is al Shabaab?

Loud explosions were heard at the Kenya mall as investigators cleared IEDs left behind from the terror attack. New pictures show the mall’s parking structure in ruins, still smoldering. Meanwhile, there is intense speculation about the “white widow.” NBC’s Ron Allen reports.

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This content comes from Closed Captioning that was broadcast along with this program.

>>>now arrive uhhuh in force. dozens are on the scene of the massacre in
nairobi
,
kenya
. the troubles news today. another attack in
kenya
. this one killed two
police officers
and the worry here, obviously, is this
terrorist groupal shabaab
is making it known that they are on the rise. and there's been an international
arrest warrant
issued for a british woman with a nickname out of a
spy novel
. she's known as the
white widow
. officials say they want to know of any involvement she might have had in what happened in
kenya
. we begin again tonight with nbc's
ron allen
in
nairobi
where there's been some activity tonight, i understand, ron.

>> reporter: indeed, brian. good evening. tonight we heard several loud explosions and saw fire at the mall site down the road behind me there. investigators say it is the hard work of clearing away ieds, bombs and explosives the militants
left behind
. the devastation of the
west gate
mall up close. new pictures
today show
the parking structure in ruins, still smoldering. what caused this much damage? authorities aren't saying. meanwhile intense speculation about this woman,
samantha lewthwaite
of britain, once married to a
london subway
bomber. she's known as the
white widow
. she may now be the most wanted woman in the world. today at
kenya
's request interpol issued a warrant for her arrest. in connection with a
2011
plot to bomb targets in ten i can't. no known connection to the mall attack but unconfirmed reports of a
white woman
among the gunmen. in
kenya
near the somalia border, another attack. two
kenyan police
officers killed.
al shabaab
again claiming responsibility. while at the mall itself investigators, including
fbi agents
, looked for clues, trying to piece together exactly what happened here.

>>this program has learned from multiple sources the identities of two of the attackers.

>> reporter: tonight a
british tv
report says a former kenyan
special forces
soldier, also a convert to islam, linked to
al shabaab
, led the assault. how big a threat is
al shabaab
?

>>groups like
al shabaab
are the new face of
al qaeda
. the attack we saw in
nairobi
represent s the worst face. what we have to make sure is that the threats re main regionally focused and not towards the west and the
united states
.

>> reporter: al shabaab
has claimed some americans participated in the mall attack, but there's been no evidence of that so far.

>>we don't have any verifiable information that would indicate one way or the other whether any americans were involved.

>> reporter: as the questions pile up,
kenya
's grief continues. there were multiple funerals again today. as people here found comfort in stories of survival uh and powerful images of heroic rescues and lives saved. tonight there is more late-breaking information regarding the case involving the so-called
white widow
. nbc news has learned
british authorities
are seeking dna samples from members of her family as the investigation moves forward. brian?